// 格式类似于 Python 中的列表
let arr = [1, 2, 3, 4, 5]

let arr1: number[] = [1, 2, 3, 4, 5]
console.log(arr1);

let arr2:Array<number> = [1, 2, 3, 4, 5]
console.log(arr2);

arr1[0] = 123
console.log(arr1);

// 未赋值的元素结果为 undefined
arr1[9] = 9
console.log(arr1);
console.log(arr1[7]);
